the brain

Honors Anatomy & Physiologyfor copying

Brain: unremarkable appearance ~ 3 lbs

4 major regions

• right & left connected by large fiber tract: corpus callosum

• cover most of other 3 parts• surface: elevated ridges = gyri

separated by shallow grooves = sulci• Fissures deeper grooves separate

regions of brain

1. Cerebral Hemisphere

• separates cerebral hemispheres• other fissures separate brain into

lobes

Longitudinal Fissure

• spaces in brain filled with CSF

• connected to subarachnoid space (around brain & spinal cord) and central canal of spinal cord

Ventricles of the Brain

• parietal lobe posterior to central sulcus

• receives impulses from sensory receptors (not special senses), interprets them– pain recognition– temperature– light touch

Somatic Sensory Area

• anterior to central sulcus in frontal lobe

• major voluntary motor tract

Primary Motor Area

• visual area

Occipital Lobe

• auditory & olfactory areas

Temporal Lobe

• Brocca’s Area: ability to speak–@ base of precentral gyrus (usually only

on left side)– injury inability to correctly vocalize

words

Frontal Lobe

• anterior frontal lobe: higher intellectual reasoning

• complex memories: frontal/ temporal lobe

• all facets of speech: occipital/temporal/parietal lobes

Lobe Functions

Gray Matter of the Brain

• gray matter in brain that is NOT in cerebral cortex

• functions: help regulate voluntary motor activity by modifying instructions sent to skeletal muscle by primary motor cortex

Basal Nuclei

2. Diencephalon

• sits atop brain stem• enclosed by cerebral hemispheres• major parts:– Thalamus– Hypothalamus– Limbic system– Epithalamus

Diencephalon

• relay station for sensory impulses passing thru to sensory cortex

Thalamus

• ANS center• role in:– temperature control– water balance–metabolism

Hypothalamus

Limbic System: forms rim surrounding corpus callosum

• regulates autonomic & endocrine functions in response to emotional stimuli (“reacting” brain vs. cerebral cortex being “thinking” brain)– set level of arousal–motivation– reinforcing behaviors– rage, love, memory, empathy

Limbic System

• ~size of thumb in diameter & ~ 3 inches long

• 3 parts:1. midbrain2. pons3. medulla oblongata

Brain Stem

• knots of capillaries w/in each ventricle

• produce & secrete CSF (cerebral spinal fluid)

Choroid Plexus

• smallest, uppermost part of brain stem

• cerebral aquaduct: tiny canal that runs thru midbrain connecting 3rd & 4th ventricles

• contains reflex centers for vision, hearing

Midbrain

• “bridge”• rounded structure that protrudes

below midbrain• contains apneustic (produces deep,

prolonged inspirations) & pneumotatic center (inhibits inspiration)

Pons

• most inferior part of brain stem• inferior border merges into spinal

cord• centers: heart rate, BP, breathing,

swallowing, vomiting

Medulla Oblongata

• large, cauliflower-like • projects dorsally from under occipital

lobe • 2 hemispheres• convoluted surface• provides precise timing for skeletal

muscle activity• Controls balance & equilibrium

Cerebellum

• Head injuries are leading cause of accidental death in USA.

• Concussion: dizziness, “see stars”, briefly lose consciousness; No permanent brain damage

• Contusion: result of marked tissue damage. Cerebrum: may maintain consciousness Brainstem: coma

• Cerebral Edema: swelling of brain due to inflammatory response to injury/ initially conscious neuro signs deteriorate (think edema or hemorrhage)

Traumatic Brain Injuries

• stroke• 3rd leading cause of death in USA• occur when blood circulation to brain

is interrupted – vessel could be blocked (temporary or

permanent) or hemorrhaging

Cerebrovascular Accident(CVA)

CVA• characterized by:– abrupt onset of persisting neurological

symptoms that arise from destruction of brain tissue

common causes:– intracerebral hemorrhage– emboli– atherosclerosis of cerebral arteries

CVA Risk Factors1. hypertension2. hypercholesterolnemia3. heart disease4. narrowed carotid arteries5. hx of TIAs (transient ischemic attacks)6. diabetes7. smoking8. obesity9. excessive alcohol intake

CVA Treatments• Thrombolytic:– clot-dissolving drug: tissue plasminogen

activator (t-PA) greatly improved prognosis for CVA

– aspirin (makes plts slippery fewer clots)– blood thinners

• Aphasia: from damage to left side cerebrum where language centers are

• Motor Aphasia:– damage to Broca’s area– loss of ability to speak

• Sensory Aphasia:– loss of ability to understand written or

spoken word

Sequelae of CVA

• Transient Ischemic Attack• “mini-stroke”• due to temporary restriction of blood

flow• symptoms last 5 – 50 minutes• “red flags” that warn impending &

more serious CVAs

TIA

Alzheimer Disease (AD)• most common type of dementia• >10% population > age 65• 4th leading cause of death in US• characterized by progressive loss of

reasoning & ability to care for oneself• cause of most cases unknown but…– genetic factors– environmental or lifestyle factors– normal aging process